環境：
CentOS 5.4 x64
這裏只用1臺虛擬機的3個不同端口模擬，可以進一步模擬3臺虛擬機的同一個端口實驗
yum -y install gcc
mkdir -p /opt/{lnmp,packet_src}/
cd /opt/packet_src/
wget https://memcached.googlecode.com/files/memcached-1.4.15.tar.gz
wget http://sourceforge.net/projects/levent/files/libevent/libevent-1.4/libevent-1.4.13-stable.tar.gz/download
wget http://memagent.googlecode.com/files/magent-0.6.tar.gz
1、編譯安裝libevent：
tar zxvf libevent-1.4.13-stable.tar.gz
cd libevent-1.4.13-stable/
./configure --prefix=/usr
make && make install
cd ../
2、編譯安裝Memcached
tar zxvf memcached-1.4.15.tar.gz
cd memcached-1.4.15/
./configure --prefix=/opt/lnmp/memcached/ --with-libevent=/usr
make && make install
cd ../
參數手冊
啓動過程中所用選項說明如下：
-p，使用的TCP端口。默認爲11211。
-m，最大內存大小。默認爲64MB。
-vv，以very vrebose模式啓動，將調試信息和錯誤輸出到控制檯。
-d，作爲守護進程在後臺運行。
-c，最大運行的併發連接數，默認是1024，按照服務器的負載量來設定。
-P，設置保存Memcache的pid文件。
-l，監聽的服務器IP地址，如果有多個地址。
-u，運行Memcached的用戶，默認不能由root用戶啓動，所以當前用戶爲root用戶時，需要利用-u參數來指定。
例：/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11211 -u root -P /opt/lnmp/memcached/memcached_11211.pid -c 256
3、編譯安裝magent：
mkdir -p magent
tar zxvf magent-0.6.tar.gz -C magent
/sbin/ldconfig
sed -i "s#LIBS = -levent#LIBS = -levent -lm#g" Makefile //版本小於0.6需要執行這一句
make
cp magent /usr/bin/magent
Usage:
-h this message
-u uid
-g gid
-p port, default is 11211. (0 to disable tcp support)
-s ip:port, set memcached server ip and port
-b ip:port, set backup memcached server ip and port
-l ip, local bind ip address, default is 0.0.0.0
-n number, set max connections, default is 4096
-D do not go to background
-k use ketama key allocation algorithm
-f file, unix socket path to listen on. default is off
-i number, max keep alive connections for one memcached server, default is 20
問題：
gcc: /usr/lib64/libevent.a: No such file or directory
解決辦法：
ln -s /usr/lib/libevent.a /usr/lib64/libevent.a
問題：
gcc -Wall -g -O2 -I/usr/local/include -m64 -o magent magent.o ketama.o /usr/lib64/libevent.a /usr/lib64/libm.a
/usr/lib64/libevent.a(event.o): In function `gettime':
/home/shuzhi/libevent-1.4.5-stable/event.c:150: undefined reference to `clock_gettime'
/usr/lib64/libevent.a(event.o): In function `detect_monotonic':
/home/shuzhi/libevent-1.4.5-stable/event.c:133: undefined reference to `clock_gettime'
解決辦法：
gcc -lrt -Wall -g -O2 -I/usr/local/include -m64 -o magent magent.o ketama.o /usr/lib64/libevent.a /usr/lib64/libm.a
實例：
/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11211 -u root -P /opt/lnmp/memcached/memcached_11211.pid -c 256
/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11212 -u root -P /opt/lnmp/memcached/memcached_11212.pid -c 256
/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11213 -u root -P /opt/lnmp/memcached/memcached_11213.pid -c 256
magent -u root -n 51200 -l 127.0.0.1 -p 12000 -s 192.168.4.222:11211 -s 192.168.4.222:11212 -b 192.168.4.222:11213
注：
1、分別在11211、11212、11213端口啓動3個Memcached進程，在12000端口開啓magent代理程序；
2、11211、11212端口爲主Memcached，11213端口爲備份Memcached；
3、連接上12000的magent，set key1和set key2，根據哈希算法，key1被寫入11212和11213端口的Memcached，key2被寫入11212和11213端口的Memcached；
4、當11211、11212端口的Memcached死掉，連接到12000端口的magent取數據，數據會從11213端口的Memcached取出；
5、當11211、11212端口的Memcached重啓復活，連接到12000端口，magent會從11211或11212端口的 Memcached取數據，由於這兩臺Memcached重啓後無數據，因此magent取得的將是空值，儘管11213端口的Memcached還有數 據（此問題尚待改進）。
測試：
# telnet 127.0.0.1 12000
Trying 127.0.0.1...
Connected to Monitor (127.0.0.1).
Escape character is '^]'.
stats
memcached agent v0.6
matrix 1 -> 192.168.4.222:11211, pool size 0
matrix 2 -> 192.168.4.222:11212, pool size 0
END
set key1 0 0 9
chinatree
STORED
set key2 0 0 9
chinatree
STORED
quit
Connection closed by foreign host.
# telnet 192.168.4.222 11211
Trying 192.168.4.222...
Connected to 192.168.4.222.
Escape character is '^]'.
get key1
VALUE key1 0 9
chinatree
END
get key2
END
quit
Connection closed by foreign host.
# telnet 192.168.4.222 11212
Trying 192.168.4.222...
Connected to 192.168.4.222.
Escape character is '^]'.
get key1
END
get key2
VALUE key2 0 9
chinatree
END
quit
Connection closed by foreign host.
# telnet 192.168.4.222 11213
Trying 192.168.4.222...
Connected to 192.168.4.222.
Escape character is '^]'.
get key1
VALUE key1 0 9
chinatree
END
get key2
VALUE key2 0 9
chinatree
END
quit
Connection closed by foreign host.
模擬11211和11212端口全down掉
kill `cat /opt/lnmp/memcached/memcached_11211.pid` `cat /opt/lnmp/memcached/memcached_11212.pid`
# telnet 127.0.0.1 12000
Trying 127.0.0.1...
Connected to Monitor (127.0.0.1).
Escape character is '^]'.
get key1
VALUE key1 0 9
chinatree
END
get key2
VALUE key2 0 9
chinatree
END
quit
Connection closed by foreign host.
恢復11211和11212端口：
/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11211 -u root -P /opt/lnmp/memcached/memcached_11211.pid -c 256
/opt/lnmp/memcached/bin/memcached -m 32m -d -l 192.168.4.222 -p 11212 -u root -P /opt/lnmp/memcached/memcached_11212.pid -c 256
# telnet 127.0.0.1 12000
Trying 127.0.0.1...
Connected to Monitor (127.0.0.1).
Escape character is '^]'.
get key1
END
get key2
END
quit
Connection closed by foreign host.
參考網址：
https://code.google.com/p/memagent/
http://simblog.vicp.net/?p=105